Succinic acid and its derivatives are widely used as specialty chemicals for applications in foods, pharmaceuticals, and cosmetics.
The Glassner et al U.S. Pat. No. 5,143,834 and the Datta et al U.S. Pat. Nos. 5,168,055, both disclose integrated processes for the production of succinic acid. These patents employed the anaerobic bacterium Anaerobiospirillum succiniciproducens (ANS) which produces comparatively low concentrations of succinic acid, approximately 35 g/1. However, commercial fermentations which are used for the bulk production of organic acids, such as citric and lactic acids, typically produce higher concentrations of acids, e.g. 80-120 g/1. Likewise, the production of high concentrations of succinic acid is needed for an economical commercial production of succinic acid.
The accumulation of very high concentrations of acids in a fermentation broth is not a normal phenomenon for microorganisms and thus the development of a commercial fermentation process usually depends on improvement of naturally occurring strains. Strain selection and strain mutation are techniques frequently used to obtain improved strains that produce high yields of organic acids. However, finding improved strains is a very difficult process, and without methods that favor and identify high producing strains it is normally necessary to examine as many as 100,000-1,000,000 clones to find even one improved strain..sup.1
It would be advantageous to have a fermentation method for producing the higher concentrations of succinic acid which are necessary for commercial production. It also would be advantageous to have microorganisms that produce higher concentrations of succinic acid and methods of selecting those microorganisms.